Dr. Peter P. Reese, a National Research Service Award Fellow in the Renal Division at the University of Pennsylvania School of Medicine, is applying for a K-23 Patient Oriented Research Career Development Award to acquire further experience and skills for an academic career as an independent investigator focused on transplantation. This proposal outlines a 5-year multi-disciplinary training program consisting of research, coursework, and mentoring by Dr. Harold I. Feldman, Director of the Clinical Epidemology Unit at Penn's Center for Clinical Epidemology and Biostatistics. Dr. Reese will pursue coursework in epidemiology, biostatistics, health policy and medical ethics which pertain directly to his proposed K-23 project, and which will prepare him to lead future independent research programs related to renal transplantation. The prevalence of end-stage renal disease (ESRD) in the United States (US) continues to climb, with devastating consequences for patients including an elevated risk of cardiovascular death and the burden of chronic dialysis. The growing ESRD population has intensified the demand for kidney transplantation, which has been shown to reduce mortality and improve quality of life compared to chronic dialysis. Given a limited supply of deceased donor kidneys, transplant professionals have increasingly focused attention on living kidney transplantation. Maximizing this vital resource for transplant candidates could substantially reduce the burdens of ESRD. Large and unexplained variation exists in the magnitude of living kidney transplantation across renal transplant centers. Comprehensive transplantation records from the United Network of Organ Sharing offer a valuable opportunity to elucidate the factors underlying this variation. Through the proposed project, Dr. Reese will measure magnitude of living kidney transplantation within and across transplant centers, and identify center attributes associated with variation in the magnitude of living kidney transplantation. Understanding how transplant centers optimize or limit their patients'opportunities to obtain a live donor kidney transplant represents a crucial advance in developing strategies to expand access to transplantation overall.